swollen pec

So yesterday i woke up and my right pec is a little bigger than my right and I can't seem to figure out why. It IS sorer than my left so Idk. This happened when I first started working out back in May and I started taking crappy creatine. This time is different. The first time it felt like I was flexing it for about 3-4 days straight.......then it stopped and I had bad water retention underneath/below my right pec. This time it doesn't feel like its flexed...but just really sore and I'm not on creatine. any ideas?

im left tricept dom. and this has happend to me in my right pec. although they are the same size, my right one tends to cramp up and start shaking awkwardly on its on when drying myself off with a towel or something after a workout